Automated assembly and welding of structures

ABSTRACT

A system for automated assembly and welding is disclosed. The system includes a pallet for receiving incoming workpieces; a workpiece holder having a plurality of electromagnets; a handling robot configured to transport incoming workpieces from the pallet to the workpiece holder; and a controller in communication with the workpiece holder and the handling robot. The controller is configured to determine an orientation of a workpiece positioned on the workpiece holder, and to selectively adjust an activation state of one or more electromagnets of the workpiece holder based upon the orientation of the workpiece. A method of assembling and welding workpieces is also disclosed.

RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 12/314,219 (now U.S. Pat. No. 8,157,155), filed Dec. 5, 2008, whichis a continuation-in-part of U.S. application Ser. No. 12/078,675, filedApr. 3, 2008 (now abandoned), the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally to automated manufacturing,and, more particularly, to an automated assembly and welding system anda method for automated assembly and welding of structures.

BACKGROUND

Robotic welding machines have been used across various industries forthe purpose of assembling and joining components. For example, roboticwelding machines have been used to weld vehicle frame componentstogether and to weld body panels to welded vehicle frames. Typically,human-operated cranes are used to transport various components to anassembly station. The components are mounted on a fixture that positionsthe components in a desired welding orientation. A robotic weldingmachine is then programmed to weld the components together as they areheld by the fixture. Although the robotic welding machine improves theefficiency and accuracy of the welding process itself, there are oftendelays and errors that result from the human-operated fixturing process.As a result, several attempts have been made at more fully automatingthe component transport, fixturing, and joining processes.

One example of an automated assembly system is described in U.S. Pat.No. 5,272,805 (the '805 patent) issued to Akeel, et al. on Dec. 28,1993. The automated assembly system of the '805 patent uses automatedguided vehicles to transport desired components to an assembly station,where a material handling robot is used to place the components on afixturing platform. The fixturing platform includes a plurality ofprogrammable robotic locators, which are programmed to receive and clampthe particular components positioned there by the material handlingrobot. Once the desired components have been clamped into theprogrammable robotic locators, a processing robot is used to weld theclamped components together.

Although the system of the '805 patent may help minimize the delays anderrors associated with human fixturing, it may not be able to properlyfixture certain shapes of components or consecutive components ofvarying sizes. Specifically, the programmable robotic locaters of the'805 patent are disposed in certain locations of the fixturing platformand they are programmed to orient themselves with respect to aparticular assembly. Therefore, they may be unable to accommodatecomponents that do not particularly match the design of the programmablerobotic locators installed on the platform. Moreover, the system of the'805 patent may require the use of numerous fixturing platforms along amanufacturing line, each fixturing platform having a particularinstallation of programmable robotic locators, which are programmed toclamp a particular assembly of components.

The disclosed systems and methods are directed to overcoming one or moreof the shortcomings in the existing technology.

SUMMARY

In one aspect, the present disclosure is directed to a system forassembling workpieces. The system includes a pallet for receivingincoming workpieces; a workpiece holder having a plurality ofelectromagnets; a handling robot configured to transport incomingworkpieces from the pallet to the workpiece holder; and a controller incommunication with the workpiece holder and the handling robot. Thecontroller is configured to determine an orientation of a workpiecepositioned on the workpiece holder, and to selectively adjust anactivation state of one or more electromagnets of the workpiece holderbased upon the orientation of the workpiece.

In another aspect, the present disclosure is directed to a method ofassembling workpieces. The method includes positioning a first workpieceon a work holding system having a plurality of electromagnets;positioning a second workpiece on the work holding system; selectivelyactivating the electromagnets to hold the first and second workpieces tothe work holding system; welding the first and second workpiecestogether; and inspecting the first and second workpieces once they arewelded together. The electromagnets are selectively adjusted based uponpositions of the first and second workpieces and based upon positions ofa welding tool used to weld the first and second workpieces together.

In yet another aspect, the present disclosure is directed to a method ofassembling workpieces. The method includes positioning a plurality ofworkpieces on a work holding system having a plurality ofelectromagnets; selectively activating the electromagnets to hold theworkpieces to the work holding system; retrieving a camera to inspectthe workpieces held to the work holding system; retrieving a weldingtorch to weld the workpieces together; and retrieving a camera toinspect the workpieces once they are welded together. The electromagnetsare selectively adjusted based upon positions of the workpieces andbased upon positions of the welding torch as it welds the workpiecestogether.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary disclosed manufacturingcell;

FIG. 2 is a top view of the exemplary disclosed manufacturing cell ofFIG. 1;

FIG. 3 is a side view of the exemplary disclosed manufacturing cell ofFIG. 1;

FIG. 4 is a diagrammatic illustration of an exemplary disclosedfabrication system for use with the exemplary manufacturing cell ofFIGS. 1-3;

FIG. 5 is a diagrammatic illustration of an exemplary disclosed workholding system for use with the exemplary fabrication system of FIG. 4;

FIG. 6 is a flow diagram illustrating an exemplary control method forusing the exemplary manufacturing cell disclosed in FIGS. 1-3; and

FIG. 7 is a flow diagram illustrating an exemplary control method forusing the exemplary fabrication system disclosed in FIG. 4.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary manufacturing cell 10. Manufacturingcell 10 may include an enclosure 12, in which manufacturing equipmentmay be disposed for handling, manipulating, machining, joining,measuring, and/or inspecting workpieces. Manufacturing cell 10 mayinclude a control system 14 disposed outside of enclosure 12, by whichone or more operators may program and control manufacturing equipmentinside enclosure 12. Enclosure 12 may include a plurality ofinterlocking gates 16 through which installers, operators, andmaintenance workers may enter and exit manufacturing cell 10. Enclosure12 may also include an interlocking, vertical-sliding load door 18,through which pallets, workpieces, and/or manufacturing equipment mayenter and exit manufacturing cell 10. Although control system 14 isdepicted outside of enclosure 12, control system 14 may also, oralternatively, be disposed inside of enclosure 12. Moreover, numerousadditional and/or alternative entry- and exit-ways are contemplatedbesides the exemplary disclosed interlocking gates 16 andvertical-sliding load door 18, as will be appreciated by one of skill inthe art.

As shown in FIG. 1, manufacturing cell 10 may include an incomingworkpiece pallet 20 and an outgoing workpiece pallet 22 disposedadjacent to vertical-sliding load door 18. Workpieces may be transportedto and from manufacturing cell 10 on incoming and outgoing workpiecepallets 20, 22, respectively. For example, a forklift apparatus,automated guided vehicle (“AGV”), gantry equipment, conveyor equipment,turntable, and/or robotic equipment may be used to transport workpiecepallets 20, 22 to and from manufacturing cell 10 throughvertical-sliding load door 18. Alternatively, such equipment may be usedto transport workpieces to and from manufacturing cell 10 without theuse of pallets. Moreover, any transport equipment used withmanufacturing cell 10 may be automated and configured to interact withcorresponding transport equipment of other manufacturing cellsconstituting part of a larger manufacturing operation.

Manufacturing cell 10 may include any type and number of manufacturingmachines within enclosure 12, such as handling, manipulating, machining,joining, measuring, and/or inspecting equipment. In one embodiment,manufacturing cell 10 may include a fabrication system 100 for automatedassembly and welding of workpieces. Specifically, fabrication system 100may include various tools to make or change structures, machines,process equipment, and/or other hardware used in a wide range ofindustries. These industries may include, for example, mining,construction, farming, power generation, transportation, or any otherindustry known in the art. It is contemplated that fabrication system100 may be used in any environment to hold any magnetic workpiece. Inone embodiment, for example, fabrication system 100 may be employed tofabricate components of a wheel loader used in the constructionindustry.

As shown in the embodiment of FIG. 1, fabrication system 100 may includea handling robot 24 and a working robot 26 configured to operate incooperation with a work holding system 28. Handling robot 24 may beconfigured to pick up workpieces arriving on incoming workpiece pallet20 and position them on work holding system 28. Working robot 26 may beconfigured to machine, join, measure, and/or inspect workpiecespositioned on work holding system 28 by handling robot 24.

FIG. 2 illustrates a top view of the manufacturing cell 10 depicted inFIG. 1. As shown in FIG. 2, control system 14 may include a power supply32, dual industrial robot controllers (“IRCs”) 34, a manufacturing cellcontroller 36, an electronics cabinet 38, and a user interface 40.Components of control system 14 may be in communication with each other,with machines of manufacturing cell 10, with machines of anothercooperating manufacturing cell, with a control room, and/or with anycommunication network, such as a local area network (“LAN”), or widearea network (“WAN”). For example, components of control system 14 maybe connected to machines of manufacturing cell 10 via electrical cablesrunning through one or more cable routing access holes 13 disposed inthe floor, ceiling, or walls of manufacturing cell 10. Alternatively,components of control system 14 may be in wireless communication witheach other and with machines of manufacturing cell 10.

Within enclosure 12, manufacturing cell 10 may include a detection unit42 positioned over incoming workpiece pallet 20. Detection unit 42 maybe any type of device configured to detect the presence, type,orientation, and/or identity of a workpiece entering enclosure 12. Forexample, detection unit 42 may include a CCD camera, a laser camera, aninfrared camera, a radar detector, a sonar detector, an optical scanner,an RFID reader, a scale, a tactile sensor, a proximity sensor, a motionsensor, an electromagnetic sensor, and/or any other suitable sensingdevice, or any combinations thereof. Detection unit 42 may be configuredto transmit data detected from an incoming workpiece to control system14 for processing. Alternatively, detection unit 42 may be configured toprocess at least part of the detected data before transmission tocontrol system 14. Accordingly, detection unit 42 and control system 14,together, may be configured to determine any desired information about aworkpiece that has arrived at manufacturing cell 10 for processing.

Handling robot 24 may be configured to reach between incoming workpiecepallet 20, work holding system 28, a calibrating park switch 44, andoutgoing workpiece pallet 22. Handling robot 24 may include an endeffector 47, which is configured to grasp and manipulate workpieces. Forexample, end effector 47 may include gripping jaws or clamps,electromagnetic devices, suction devices, adhesive devices, or any othersuitable workpiece handling device. Handling robot 24 may be configuredto dock its end effector 47 at park switch 44 for the purpose ofstoring, calibrating, and/or locating end effector 47 relative to aknown point.

Working robot 26 may be configured to reach between work holding system28 and a tool changing station 50. Working robot 26 may be configured tomachine, join, measure, and/or inspect workpieces positioned on workholding system 28 by handling robot 24. Working robot 26 may include anytype of end effector 48 which is desired to be used for these purposes,such as, for example, a saw, a milling tool, a drill, a laser cutter, anelectron discharge machine (EDM), a welding torch, a soldiering tool, anadhesive applicator, a CCD camera, a tactile sensor, or any othersuitable robotic end effector. Tool changing station 50 may beconfigured to facilitate exchanges between different end effectors 48 ofworking robot 26. Tool changing station 50 may also include a parkswitch for storing, calibrating, and/or locating end effector 48 ofworking robot 26 relative to a known point. In the event that workingrobot 26 is provided with a welding torch, working robot 26 may also beprovided with automated welding mechanisms including floor-mounted wirespools 52 and stand-mounted wire feeders 54, both of which may beintegrally controlled by control system 14 for supplying welding wire toa welding torch installed on working robot 26.

Manufacturing cell 10 may also include a tool finding system 46. Toolfinding system 46 may be a tool center point (“TCP”) system configuredto locate and calibrate locations of end effectors 47, 48 of handlingrobot 24 and working robot 26, respectively. For example, tool findingsystem 46 may be configured to determine both a three-dimensionallocation and an angle of end effectors 47, 48. Tool finding system 46may be configured to transmit end effector orientation data directly tocontrol system 14 for processing, or it may perform at least someanalysis of end effector orientation data before transmitting it tocontrol system 14. In some embodiments, tool finding system 46 may alsobe configured to determine a three-dimensional location and orientationof one or more workpieces positioned on work holding system 28.

FIG. 3 is a side view of the exemplary manufacturing cell 10 depicted inFIGS. 1 and 2. FIG. 3 illustrates detection unit 42 positioned overincoming workpiece pallet 20 adjacent to vertical-sliding load door 18.FIG. 3 also illustrates side views of handling robot 24, working robot26, and their respective end effectors 47, 48. FIG. 3 also illustratesside views of tool finding system 46 aligned with work holding system28; tool changing station 50 aligned with working robot 26; andfloor-mounted wire spools 52 and stand-mounted wire feeders 54corresponding to working robot 26.

FIG. 4 illustrates an exemplary embodiment of a fabrication system 100,which may be advantageously incorporated in the manufacturing cell 10disclosed in FIGS. 1-3. As shown in the embodiment of FIG. 4,fabrication system 100 may include a working robot 26, a work holdingsystem 28, a first power source 120, a second power source 122, and acontroller 140.

As shown in FIG. 4, work holding system 28 may be an electromagneticwork holding system and may be configured to secure a first magneticworkpiece 114 and a second magnetic workpiece 115 during variousfabrication processes. For example, first magnetic workpiece 114 andsecond magnetic workpiece 115 may be secured by work holding system 28for an arc welding process. Work holding system 28 may include a surfacemember 116 and a plurality of electromagnets 112 to secure magneticworkpieces 114, 115 to surface member 116. Each electromagnet 112 may beassociated with a cutout 118 and may or may not be disposed, at leastpartially, within surface member 116. It is contemplated that eachelectromagnet 112 may or may not be flush with surface member 116. Ifeach electromagnet 112 is not flush with surface member 116, a gap 255may exist between the top of each electromagnet 112 and surface member116. Gap 255 may provide a pocket of air to insulate each electromagnet112 from any heat generated by the fabrication process.

Each electromagnet 112 may be a conventional electromagnet as known inthe art and may be connected to a base plate 215. Base plate 215 may beconstructed of an electrically conducting material, such as, forexample, steel. Base plate 215 and surface member 116 may be included toprovide a structural support to connect each electromagnet 112 to workholding system 28. For example, each electromagnet 112 may be bolted,riveted, welded, or fastened to base plate 215 using any other methodapparent to one skilled in the art.

Each electromagnet 112 may have an activated state and a deactivatedstate and these states may be selectively adjusted by controller 140. Inthe activated state, an electrical energy may flow from first powersource 120 to electromagnets 112 and may generate a magnetic fieldaround each electromagnet 112. In the deactivated state, the magneticfield may be reduced from the activated state or may be eliminated byslowing or stopping the flow of electrical energy to each electromagnet112 from first power source 120. It is contemplated that electricalenergy supplied to each electromagnet 112 may be reversed for a shortperiod of time prior to reducing or stopping the flow of electricalenergy. This reversal of the flow of electrical energy may help toeliminate a residual magnetic field. It is further contemplated that theactivation state of each electromagnet 112 may be selectively adjustedand that only electromagnets in the vicinity of magnetic workpieces 114,115 may be commanded into an activated state by controller 140.

The magnetic field generated by each electromagnet 112 in an activatedstate may be strong enough to cause arc blow during the arc weldingprocess. As such, each electromagnet 112 within a predefined proximityto the fabrication process may be selectively adjusted into adeactivated state. Alternatively, electromagnets outside of thepredetermined proximity to the fabrication process may be commanded intoan activated state to secure magnetic workpieces 114, 115 to surfacemember 116. It is contemplated that a variety of methodologies may beemployed to activate and deactivate each electromagnet 112. For example,controller 140 may employ a rectangular coordinate system and track anarc welder performed automated fabrication process with respect to knownlocations of each electromagnet 112. Additionally or alternatively,sensors may be associated with the plurality of electromagnets 112 tosense a change in various parameters. Controlling the activation stateof each electromagnet 112 will be discussed with respect to controller140 below.

Work holding system 28 may also include a web plate 220, openings 250, agrounding plate 240 (shown in FIG. 5), and a plurality of hard stops330. Web plate 220 may be constructed of an electrically conductingmaterial such as, for example, steel. Web plate 220 may be disposedbetween surface member 116 and base plate 215 to provide structuralrigidity to work holding system 28.

Web plate 220 may include various openings 250. Openings 250 may allowair to flow between surface member 116 and base plate 215 therebyallowing work holding system 28 to be cooled by convection. For example,gap 255 may facilitate convection by allowing a flow of air to passbetween surface member 116 and base plate 215. It is contemplated that acooling device may be added to work holding system 28 to facilitatecooling by forced convection. For example, the cooling device mayfacilitate cooling by forced convection using compressed air or mayemploy a fan to draw air flow through openings 250.

Grounding plate 240 may be connected to base plate 215 or any otherconducting portion of work holding system 28 to direct an electricalcurrent to second power source 122 through work holding system 28. Forexample, the electrical current may be conducted by base plate 215, webplate 220, surface member 116, and first magnetic workpiece 114 from anelectrode tip 155. It is contemplated that grounding plate 240 may beomitted and an arc welding process may be directed through a secondelectrode (not shown) attached to working robot 26.

Hard stop 330 may be connected to work holding system 28 via base plate215, web plate 220, linkage 328, and/or surface member 116. Hard stop330 may by any block, flange, pin, or other hard surface configured toprotrude above surface member 116, and be used to restrict movement offirst magnetic workpiece 114. Further, hard stop 330 may also be use toalign first magnetic workpiece 114. For example, first magneticworkpiece 114 may be positioned against hard stop 330 to align firstmagnetic workpiece 114 with respect to surface member 116 for thefabrication process. The vertical and horizontal location of hard stop330 may also be reconfigured through the use of linkage 328, which mayinclude any combination of gears, bearings, and/or linear drivesconfigured to selectively position hard stop 330 relative to workholding system 28. Thus, linkage 328 may be used to control thepositioning of workpieces aligned by hard stop 330. It will beappreciated that work holding system 28 may include any quantity ororientation of hard stops 330, as desired for aligning workpieces onwork holding system 28.

Working robot 26 may include hardware associated with a welding, amachining, a cutting, and/or an assembly process. For example, workingrobot 26 may include hardware associated with arc welding, plasmacutting, or any other hardware known to one skilled in the art to beaffected by electromagnetic fields. In the embodiment shown in FIG. 4,working robot 26 may include an arc welding machine having an electrodetip 155 operably attached to a robotic effector arm 150 to perform anautomated arc welding process.

Robotic effector arm 150 may be capable of moving and manipulatingelectrode tip 155 of working robot 26 through space. Robotic effectorarm 150 may include various hydraulic and electrical componentsconfigured to adjust a position of electrode tip 155. Further, movementof robotic effector arm 150 may be commanded by controller 140, whichmay be in communication with other components of control system 14.Electrode tip 155 may be used to pass a flow of electrical energythrough first magnetic workpiece 114 to shape, join, cut, or otherwisemanipulate first magnetic workpiece 114. It is contemplated thatelectrode tip 155 may receive the flow of electrical energy from secondpower source 122 through an electrical line 136. Further, it iscontemplated that working robot 26 may include a consumable or nonconsumable electrode. One skilled in the art will recognize that roboticeffector arm 150 and electrode tip 155 may embody various configurationsand may include various additional components which may be used to moveelectrode tip 155 through space. It is contemplated that working robot26 may include any conventional apparatus configured to manipulatemagnetic workpieces 114, 115.

First power source 120 may provide a source of electrical energy to workholding system 28 via an electrical supply line 121. It is contemplatedthat first power source 120 may provide various sources of electricalenergy and that those sources may be either alternating current ordirect current. For example, first power source 120 may be connected toprovide electrical energy to controller 140 via electrical supply line142. It is further contemplated that work holding system 28 and workingrobot 26 may be connected to the same power source.

Controller 140 may embody a single microprocessor, or multiplemicroprocessors for controlling and operating components of fabricationsystem 100. Numerous commercially available microprocessors may beconfigured to perform the functions of controller 140. It should beappreciated that controller 140 could readily embody a generalmicroprocessor capable of controlling numerous operating functions.Controller 140 may include a memory, a secondary storage device, aprocessor, and any other components for running an application. Variousother circuits may be associated with controller 140 such as a powersource circuit, a signal conditioning circuit, and other types ofcircuits. Controller 140 may communicate with work holding system 28 viaa work holding system communication line 134 and to working robot 26 viaa fabrication apparatus communication line 132.

One or more maps relating various system parameters may be stored in thememory of controller 140. Each of these maps may include a collection ofdata in the form of tables, graphs, equations and/or another suitableform. The maps may be automatically or manually selected and/or modifiedby controller 140 to affect movement of working robot 26 or activationstate of each electromagnet 112. For example, one such map, that is, acontrol map, may include a predetermined adjustment sequence. That is,the controller may include a collection of commands associated with themovement of electrode tip 155. That is, the control map may be storedwithin the memory of controller 140 and may include commands for aspecific welding process. The specific welding process may containvarious collections of information such as the size and location of themagnetic workpieces 114, 115 with respect to the work holding system 28.In an addition, controller 140 may also include a positional map. Thepositional map may include the relative positions of each electromagnet112, that is, the positional maps may include the position of eachelectromagnet 112 disposed within the work holding system 28.

Controller 140 may be configured to selectively adjust the activationstate of each electromagnet 112 and each hard stop 330. For example,after magnetic workpieces 114, 115 have been positioned with respect towork holding system 28, controller 140 may activate one or moreelectromagnets 112. Upon securing magnetic workpieces 114, 115 to thework holding system 28, controller 140 may command operation of thefabrication process. In this example, controller 140 may commandoperation of an arc welding process or a material removal process from afirst position 370 to a second position 371. That is, controller 140 maycommand electrode tip 155 to weld magnetic workpieces 114, 115 fromfirst position 370 to second position 371 while welding magneticworkpieces 114, 115 together. Controller 140 may also be used to controlthe location of hard stops 330, for example, based on workpiecepositions and welding processes, as desired.

By using a coordinate system and comparing the commands within thecontrol map against the positional map, controller 140 may be able todetermine a movement of electrode tip 155 to a position within thepredetermined proximity of a first electromagnet 380. Upon making thisdetermination, controller 140 may command first electromagnet 380 intothe deactivated state. While in the deactivated state, firstelectromagnet 380 may not generate a strong magnetic field and, thus maynot adversely affect the arc welding process. As the electrode tip 155moves out of the predetermined proximity of the first electromagnet 380and into the predetermined proximity of a second electromagnet 381,first electromagnet 380 may be commanded into the activated state andsecond electromagnet 381 may be commanded into the deactivated state.

In addition to and/or alternatively, work holding system 28 may includea sensor associated with the plurality of electromagnets 112. Thesesensors may be configured to sense a change in parameters indicative oftool position, such as, for example, a change in temperature. That is, atemperature sensor 375 may be associated each electromagnet 112 and maygenerate a signal based on a change in temperature associated with thearc welding process and may be disposed within the predeterminedproximity of each electromagnet 112. Because the arc welding processgenerates heat as it welds, temperature sensor 375 may detect a rapidincrease in temperature as electrode tip 155 enters the predeterminedproximity. It is contemplated there may be fewer temperature sensors 375than electromagnets 112, for example, one temperature sensor 375 may beassociated with more than one electromagnet 112. It is furthercontemplated that controller 140 may adjust the activation state ofmultiple electromagnets 112 based on a signal from one temperaturesensor or visa versa.

The signals generated by temperature sensor 375 may be directed towardcontroller 140. Controller 140 may determine, based upon the signal,that an arc welding process has entered the predetermined proximity.Upon determining that the arc welding process has entered thepredetermined proximity, controller 140 may selectively deactivate eachelectromagnet 112 associated with temperature sensor 375. Likewise, whenelectrode tip 155 moves away from temperature sensor 375, thetemperature may drop and temperature sensor 375 may then generate asignal indicative of a reduced temperature. Upon receiving the signalindicative of a reduced temperature, controller 140 may command eachelectromagnet 112 associated with temperature sensor 375 into theactivated state. It is contemplated that controller 140 may use maps inconjunction with an automated fabrication process and may usetemperature sensor 375 in conjunction with either an automatedfabrication process or a manual fabrication process. It is furthercontemplated that work holding system 28 may be fixed, for example, to atable, work bench, or other relatively stable structure, or may be fixedto a moveable structure such as, for example a robotic arm.

FIG. 5 illustrates work holding system 28 attached to a robotic effectorarm 200. Robotic effector arm 200 may be configured to move work holdingsystem 28 and manipulate first magnetic workpiece 114 (FIG. 4) throughspace. It is contemplated that robotic effector arm 200 may move firstmagnetic workpiece 114 with respect to electrode tip 155 (FIG. 4) orthat both robotic effector arm 200 and electrode tip may move withrespect to a fixed point of reference.

As previously described above with respect to working robot 26, roboticeffector arm 200 may include various hydraulic and electrical componentsand may be commanded by controller 140 to move work holding system 28.In addition to the components shown in FIG. 4, work holding system 28may also include various other components. Particularly, work holdingsystem 28 may include a liquid cooling device 230.

Liquid cooling device 230 may be disposed between an electricalinsulator (not shown) and work holding system 28. The electricalinsulator may be constructed of a thermal plastic and may be sensitiveto the high temperatures created by the arc welding process. Liquidcooling device 230 may be configured to cool the electrical insulatorand may include various components to remove heat. For example, liquidcooling device 230 may circulate water through a vane (not shown) toremove heat from work holding system 28. It is contemplated that variousdevices may be configured to cool work holding system 28 and and/orrobotic effector arm 200, or that liquid cooling device 230 may beomitted.

It is contemplated that additionally or alternatively, working robot 26may embody various tools for various other fabrication processes. Thesefabrication processes may include welding, machining, cutting, assembly,or any other fabrication process known in the art. For example,electrode tip 155 may be replaced with a cutting bit for a machiningprocess. In this example, electromagnets 112 may switch from theactivated state to the deactivated state as disclosed above so that themachine process may not be adversely affected by magnetic fields.Specifically, electromagnets 112 may be switched to the deactivatedstate so that magnetic workpieces 114, 115 may not collect debris duringthe machining process. Further, liquid cooling device 230 may beincluded and may remove heat associated with the friction caused duringthe machining process.

INDUSTRIAL APPLICABILITY

Manufacturing cell 10 and fabrication system 100 may be used to make orchange structures, machines, equipment, and/or other hardware orworkpieces for a wide range of industries. These industries may include,for example, mining, construction, farming, power generation,transportation, or any other industry known in the art. It iscontemplated that manufacturing cell 10 may be incorporated into anymanufacturing operation. For example, manufacturing cell 10 may beintegrated with a plurality of other similar or alternativemanufacturing cells as part of a large-scale assembly line. However, itwill also be appreciated that manufacturing cell 10 may be configured tomanufacture an entire component or assembly of components, without theassistance of any external manufacturing equipment. For example,manufacturing cell 10 may be implemented as a small-batch, customizationor just-in-time (“JIT”) manufacturing process configured to produce anintermediate or final product. Thus, the exemplary disclosed systems mayprovide for improved manufacturing processes, the operation of whichwill now be explained with respect to exemplary method 500.

Referring now to FIG. 6, a method 500 of assembling and weldingworkpieces may begin with the creation of control programs using anoff-line computer (Step 501). An operator may use any suitable type ofcomputer software for designing components, planning manufacturingsteps, programming robotic operations, and programming any portion ofcontrol system 14 of manufacturing cell 10. For example, the operatormay use CAD/CAM software to plan robotic manufacturing processes. Theoperator may transfer these control programs from a computer to controlsystem 14 via Ethernet, or any other suitable communication network ordata storage device (Step 502).

Once control system 14 has been provided with suitable control programs,method 500 may begin operating manufacturing cell 10 to receive andprocess workpieces by executing an incoming parts camera routine (Step504). Specifically, one or more workpieces may enter manufacturing cell10 through vertical-sliding load door 18 on an incoming workpiece pallet20. Detection unit 42 may collect data regarding a workpiece positionedon incoming workpiece pallet 20 and send it to control system 14.Detection unit 42 and/or control system 14 may then identify one or moreparts positioned on incoming workpiece pallet 20 and determine whetherat least one of the parts is correct for a desired routine (Step 506).For example, control system 14 may locate corners, or any otherdistinguishing features of a part, using data collected by detectionunit 42. A part may be correct if it is desired to be placed on workholding system 28 by working robot 24 for assembly with another part. Ifthere are no correct parts on incoming workpiece pallet 20, controlsystem 14 may create an error report (Step 558) and prompt an operatorto evaluate the error and take corrective action (Step 560).

If there is at least one correct part on incoming workpiece pallet 20,handling robot 24 may pick up the part using its end effector 47 (Step508). For example, handling robot 24 may activate one or moreelectromagnets in its end effector 47 and then contact the correct part.Working robot 26 may then perform an inspection camera routine on thepart being handled by handling robot 24 (Step 510). For example, endeffector 48 of working robot 26 may retrieve a CCD camera from toolchanging station 50 and use it to identify the part and its orientationrelative to end effector 47 or another known point. Handling robot 24may then place the part on a magnetic table, such as the work holdingsystem 28 described with respect to FIG. 4 (Step 512). Specifically,handling robot 24 may either orient the part relative to work holdingsystem 28 for it to be desirably mated with a subsequent part, orrelative to a part already positioned on work holding system 28.

If there are any parts already positioned on work holding system 28, towhich the part is desired to be joined, working robot 26 may then tackweld the two parts together, in their desired orientations as situatedby handling robot 24 and work holding system 28 (Step 514).Specifically, working robot 26 may retrieve a welding torch from toolchanging station 50. Working robot 26 may begin tack welding one or moreparts by touch sensing the part locations and orientations. Workingrobot 26 may then make a plurality of short welds in predeterminedintervals along the length of a desired weld interface so as to form atacked part assembly. This step of welding may be performed incooperation with each of handling robot 24, working robot 26, workholding system 28, and control system 14, as will be described morespecifically with respect to FIG. 7. For instance, electromagnetsassociated with work holding system 28 may be modulated depending on thelocation of a welding torch manipulated by working robot 26. Controlsystem 14 may monitor current, voltage, wire feed speed, and gas flow asworking robot 26 performs welding with its end effector 47. Controlsystem 14 may then determine whether there are any additional parts toassemble (Step 516). If there are additional parts to assemble to thetacked part assembly positioned on work holding system 28, then controlsystem 14 may return to either the incoming parts camera routine (Step504) or the handling robot pick-up routine (Step 508). Specifically,handling robot 24 may pick up another part from incoming workpiecepallet 20 based on part data obtained during the previous part pick-upprocess (Step 508), or control system 14 and detection unit 42 mayperform another incoming parts routine (Step 504).

If there are no additional parts to assemble to the tacked part assemblypositioned on work holding system 28, then handling robot 24 may pick upand re-position the tacked part assembly on work holding system 28 (Step518). Specifically handling robot 24 may position the tacked partassembly on work holding system 28 in a way that facilitates inspectionof the tacked part assembly. Working robot 26 may then perform aninspection camera routine on the tacked part assembly (Step 520). Forexample, end effector 48 of working robot 26 may retrieve a CCD camerafrom tool changing station 50 in order to measure tacked part dimensionsand assembly dimensions. Thus, working robot 26 may measure thecompliance of the tacked part assembly relative to accepted tolerances,as well as the extent of any distortion resulting from the assemblyprocess. Control system 14 may then determine whether the tacked partassembly is acceptable and whether all tack welds are within apredetermined quality threshold (Step 522). If either the tacked partassembly or tack welds are not acceptable, then control system 14 maycreate an error report (Step 558).

If the tacked part assembly and tack welds are acceptable, then workingrobot 26 may proceed with fully welding the part assembly, as desired(Step 524). Specifically, working robot 26 may retrieve a welding torchfrom tool changing station 50 and weld all desired interfaces betweenparts of the tacked part assembly. This step of welding may be performedin cooperation with each of handling robot 24, working robot 26, workholding system 28, and control system 14, as will be described morespecifically with respect to FIG. 7. For instance, electromagnetsassociated with work holding system 28 may be modulated depending on thelocation of a welding torch manipulated by working robot 26. Controlsystem 14 may monitor current, voltage, wire feed speed, and gas flow asworking robot 26 performs welding with its end effector 47. Controlsystem 14 may then determine whether all desired welds have been made(Step 526). If all desired welds have been completed, then working robot26 may perform another inspection camera routine (Step 528). Forexample, end effector 48 of working robot 26 may retrieve a CCD camerafrom tool changing station 50 in order to measure part dimensions andassembly dimensions of the welded part assembly. Control system 14 maythen determine whether the welded part assembly is acceptable andwhether all welds are within a predetermined quality threshold (Step530). If either the welded part assembly itself or its welds are notacceptable, then control system 14 may create an error report (Step558).

If the welded part assembly and welds are acceptable, then handlingrobot 24 may re-position the welded part assembly on work holding system28, as desired (Step 532). In one embodiment, control system 14 may thendetermine whether there are additional manufacturing processes toperform on the welded part assembly, such as, for example, whether thereare any parts to attach to the assembly by means other than welding(Step 534). If there are no additional manufacturing processes toperform on the welded part assembly, then control system 14 may create aconformance report (Step 554) and a transport system may deliver thefinished part to other pull systems of a larger manufacturing process(Step 556). For example, handling robot 24 may pick up the welded partassembly and position it on outgoing workpiece pallet 22, by which itmay leave manufacturing cell 10.

If there are additional manufacturing processes to perform on the weldedpart assembly, such as the adhesion of attachments to the weldedassembly, handling robot 24 may pick up an attachment, for example, fromincoming workpiece pallet 20 (Step 536). Although exemplary method 500will be described with respect to adhesion of additional attachments tothe welded assembly, one of skill in the art will appreciate that anyother desired manufacturing process may be performed on the weldedassembly. For example, the welded assembly may be machined, drilled,heat treated, and/or coated. Once handling robot 24 has retrieved anattachment to adhere to the welded assembly, handling robot 24 may takethe attachment to one or more adhesive dispensing stations (notdepicted) (Step 538). In one embodiment, at least one of the adhesivedispensing stations may dispense acrylic adhesive on the attachment(Step 540), and at least another one of the adhesive dispensing stationsmay dispense an activator on the attachment where the acrylic adhesivewas dispensed on the attachment (Step 542). The adhesive may betoughened acrylic adhesive, thermosetting adhesive, elastomericadhesive, pressure sensitive adhesive, and/or rapid setting adhesive,for example. Handling robot 24 may then press the adhesive surface ofthe attachment against a desired portion of the welded assembly (Step544). If there additional attachments to adhere to the welded assembly,handling robot 24 may pick up another attachment to adhere (Step 536).

If all of the desired attachments are in place, then working robot 26may perform another inspection camera routine (Step 548). For example,end effector 48 of working robot 26 may use a CCD camera to measureattachment dimensions and assembly dimensions. Thus, working robot 26may measure the compliance of the welded part assembly and attachmentsin relation to accepted tolerances and determine the extent of anydistortion resulting from the assembly process. Control system 14 maythen determine whether the welded part assembly and attachments areacceptable and within a predetermined quality threshold (Step 550). Ifthe welded part assembly and attachments are not acceptable, thencontrol system 14 may create an error report (Step 558). If the weldedpart assembly and attachments are acceptable, then control system 14 maycreate a conformance report (Step 554) and a transport system maydeliver the finished part to other pull systems of a largermanufacturing process (Step 556). For example, handling robot 24 maypick up the welded assembly and position it on outgoing workpiece pallet22, by which it may leave manufacturing cell 10.

Thus, method 500 may be an advantageous method of using manufacturingcell 10 for assembling and welding a plurality of workpieces in anefficient and automated manner. Because the components of manufacturingcell 10 may be fully automated, it may advantageously improve theefficiency, precision, and accuracy of machining and assemblingprocesses carried out therein. Moreover, because fabrication system 100may include a handling robot 24 and a working robot 26 operating incooperation with work holding system 28, the need for dedicatedfixturing may be eliminated.

Fabrication system 100 may be used in any environment to hold anymagnetic workpiece. For example, the disclosed method and apparatus maybe used with processes that may be adversely affected by magneticfields. As disclosed above, work holding system 28 may employ one ormore electromagnets 112 that are configured to be individually activatedby controller 140 between at least two activation states. Eachelectromagnet 112 commanded into the activated state may generate amagnetic field to hold first magnetic workpiece 114 to surface member116. Conversely, when commanded into the deactivated state, eachelectromagnet 112 may not generate the electromagnetic field and, thus,may not interfere with the arc welding process or another fabricationprocess.

Referring now to the method 400 of FIG. 7, beginning with eachelectromagnet 112 in the deactivated state, first magnetic workpiece 114may be positioned onto work holding system 28. For this example, workholding system 28 may embody a workbench. In this embodiment, firstmagnetic workpiece 114 may be positioned onto the workbench against hardstop 330. Once first magnetic workpiece 114 is in place, eachelectromagnet 112 may be commanded into the activated state bycontroller 140 (Step 405). After electromagnets 112 have been commandedinto the activated state, a fabrication process may begin, for thisexample, the fabrication process may be arc welding. It is contemplatedthat only electromagnets 112 within a proximity of magnetic workpieces114, 115 may be activated. Further, electromagnets 112 that are notpositioned within the proximity of the magnetic workpieces 114, 115 mayremain in a deactivated state.

As the arc welding process begins, controller 140 may command movementof electrode tip 155 with respect to the workbench and first magneticworkpiece 114. As electrode tip 155 comes into the proximity of eachactivated electromagnet 112, each electromagnet 112 may be commandedinto a deactivated state. For example, referring to FIG. 4, as electrodetip 155 comes into the proximity of first electromagnet 380, firstelectromagnet 380 may be commanded into the deactivated state untilelectrode tip 155 leaves the proximity of first electromagnet 380.

Controller 140 may be programmed to weld various magnetic workpiecessecured to work holding system 28 by one or more electromagnets 112.Welding commands may be read from one or more maps stored within thememory of controller 140. Controller 140 may command movement of workingrobot 26 (Step 410) from first position 370 to second position 371 (seeFIG. 4). To control the movement of working robot 26, a coordinatesystem may be used. In addition to moving electrode tip 155, thecoordinate system may also be used by controller 140 to determine theposition of electrode tip 155 with respect to each electromagnet 112(Step 415). Particularly, if controller 140 determines that electrodetip 155 is within the proximity of one or more electromagnets 112,controller 140 may command each electromagnet 112 to deactivate. Forexample, as electrode tip 155 moves from first position 370 to secondposition 371 it may come into the proximity of first electromagnet 380and second electromagnet 381.

When controller 140 determines that electrode tip 155 is within theproximity of first electromagnet 380 and/or second electromagnet 381,controller 140 may selectively switch first and/or second electromagnets380, 381 to the deactivated state (Step 420). While in the deactivatedstate, first and/or second electromagnets 380, 381 may not generate themagnetic field and, therefore, may not adversely affect the weldingprocess. After controller 140 has commanded electrode tip 155 to moveout of the proximity of first and/or second electromagnet 380, 381,first and/or second electromagnet 380, 381 may be reactivated (Step430). That is, first and/or second electromagnets 380, 381 may becommanded back into the activated state. It is contemplated thatcontroller 140 may selectively activate and deactivate any number ofelectromagnets 112 that may be affected by electrode tip 155. Suchdeactivating may occur consecutively as electrode tip 155 moves acrossmagnetic workpieces 114, 115. Further, a plurality of electromagnets 112or all of the potentially affected electromagnets 112 may be deactivatedas electrode tip 155 does work on the magnetic workpieces 114, 115. Ineach case, controller 140 will leave enough electromagnets activated sothat the magnetic workpieces 114, 115 remains adequately secured to workholding system 28. It is further contemplated that work holding system28 may be combined with the robotic effector arm 200 as shown in FIG. 5.Robotic effector arm 200 may be commanded by controller 140 to move workholding system 28 and an attached magnetic workpiece with respect toanother work holding system 28 or with respect to an electrode tip 155.

As described herein, each electromagnet 112 may be selectively activatedand selectively deactivated by controller 140. It is contemplated thatchanging the activation state of electromagnets 112 may include reducingthe magnetic field strength, reversing the magnetic field polarity oreliminating the magnetic field completely. Since controller 140 mayselectively adjust the activation state of each electromagnet 112,adverse affects caused by the magnetic fields generated by eachelectromagnet 112 on fabrication processes may be avoided. For example,the disclosed method and apparatus may reduce or eliminate arc blowduring arc welding processes. This reduction or elimination of arc blowmay reduce excessive spatter, incomplete fusion, and weld porosity.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed assembly,welding, and work holding systems without departing from the scope ofthe disclosure. Other modifications will be apparent to those skilled inthe art from consideration of the specification and practice of theassembly, welding, and work holding systems disclosed herein. It isintended that the specification and examples be considered as exemplaryonly, with a true scope of the invention being indicated by thefollowing claims and their equivalents.

1. A method of assembling workpieces, the method comprising: positioninga first workpiece on a work holding system having a plurality ofelectromagnets; positioning a second workpiece on the work holdingsystem; selectively activating the electromagnets to hold the first andsecond workpieces to the work holding system; welding the first andsecond workpieces together; and inspecting the first and secondworkpieces once they are welded together; wherein the electromagnets areselectively adjusted based upon positions of the first and secondworkpieces and based upon positions of a welding tool used to weld thefirst and second workpieces together.
 2. The method of claim 1, furthercomprising the step of: configuring hard stops on the work holdingsystem before positioning the first workpiece on the work holdingsystem; wherein the step of welding the first and second workpiecestogether comprises: tack welding the first and second workpiecestogether; inspecting the first and second workpieces once they are tackwelded together; and welding the first and second workpieces together ifthe inspected tack welding surpasses a predetermined quality threshold.3. The method of claim 2, wherein the step of inspecting the first andsecond workpieces once they are tack welded together comprises:manipulating the first and second workpieces using a handling robot; andviewing the first and second workpieces using a CCD camera manipulatedby a working robot.
 4. The method of claim 1, further comprising:positioning a third workpiece adjacent to one of the first and secondworkpieces; tack welding the third workpiece to one of the first andsecond workpieces; inspecting the first, second, and third workpiecesonce they are tack welded together; and welding the third workpiece toone of the first and second workpieces if the inspected tack weldingsurpasses a predetermined quality threshold.
 5. The method of claim 4,wherein the step of inspecting the first, second, and third workpiecesonce they are tack welded together comprises: manipulating the first,second, and third workpieces using a handling robot; and viewing thefirst, second, and third workpieces using a CCD camera manipulated by aworking robot.
 6. The method of claim 1, further comprising: applyingadhesive to a third workpiece; and pressing the third workpiece againstone of the first and second workpieces so as to adhere the thirdworkpiece to one of the first and second workpieces.
 7. A method ofassembling workpieces, the method comprising: positioning a plurality ofworkpieces on a work holding system having a plurality ofelectromagnets; selectively activating the electromagnets to hold theworkpieces to the work holding system; retrieving a camera to inspectthe workpieces held to the work holding system; retrieving a weldingtorch to weld the workpieces together; and retrieving a camera toinspect the workpieces once they are welded together; wherein theelectromagnets are selectively adjusted based upon positions of theworkpieces and based upon positions of the welding torch as it welds theworkpieces together.
 8. The method of claim 7, wherein positioning ofthe workpieces is performed by a handling robot; and retrieving of thecamera and welding torch is performed by a working robot.
 9. The methodof claim 8, wherein the selective adjustment of the electromagnets isbased upon commands sent by a controller to at least one of the handlingrobot, working robot, and work holding system.
 10. The method of claim9, wherein the selective adjustment of the electromagnets is based upona predetermined adjustment sequence stored in a memory of thecontroller.
 11. The method of claim 7, further comprising the step of:configuring hard stops on the work holding system before positioning thefirst workpiece on the work holding system; wherein the step ofretrieving a welding torch to weld the workpieces together comprisestack welding the first and second workpieces together; inspecting thefirst and second workpieces once they are tack welded together; andwelding the first and second workpieces together if the inspected tackwelding surpasses a predetermined quality threshold.
 12. The method ofclaim 7, further comprising: positioning a third workpiece adjacent toone of the first and second workpieces; tack welding the third workpieceto one of the first and second workpieces; inspecting the first, second,and third workpieces once they are tack welded together; and welding thethird workpiece to one of the first and second workpieces if theinspected tack welding surpasses a predetermined quality threshold. 13.The method of claim 12, wherein the step of inspecting the first,second, and third workpieces once they are tack welded togethercomprises: manipulating the first, second, and third workpieces using ahandling robot; and viewing the first, second, and third workpiecesusing a CCD camera manipulated by a working robot.
 14. The method ofclaim 7, further comprising: applying adhesive to a third workpiece; andpressing the third workpiece against one of the first and secondworkpieces so as to adhere the third workpiece to one of the first andsecond workpieces.
 15. A method of assembling workpieces, the methodcomprising: positioning a first workpiece on a work holding systemhaving a plurality of electromagnets; positioning a second workpiece onthe work holding system; selectively activating the electromagnets tohold the first and second workpieces to the work holding system; andwelding the first and second workpieces together; wherein theelectromagnets are selectively adjusted based upon positions of thefirst and second workpieces and based upon positions of a welding toolused to weld the first and second workpieces together.
 16. The method ofclaim 15, further comprising the step of: configuring hard stops on thework holding system before positioning the first workpiece on the workholding system; wherein the step of welding the first and secondworkpieces together comprises: tack welding the first and secondworkpieces together; inspecting the first and second workpieces oncethey are tack welded together; and welding the first and secondworkpieces together if the inspected tack welding surpasses apredetermined quality threshold.
 17. The method of claim 16, wherein thestep of inspecting the first and second workpieces once they are tackwelded together comprises: manipulating the first and second workpiecesusing a handling robot; and viewing the first and second workpiecesusing a CCD camera manipulated by a working robot.
 18. The method ofclaim 15, further comprising: positioning a third workpiece adjacent toone of the first and second workpieces; tack welding the third workpieceto one of the first and second workpieces; inspecting the first, second,and third workpieces once they are tack welded together; and welding thethird workpiece to one of the first and second workpieces if theinspected tack welding surpasses a predetermined quality threshold. 19.The method of claim 18, wherein the step of inspecting the first,second, and third workpieces once they are tack welded togethercomprises: manipulating the first, second, and third workpieces using ahandling robot; and viewing the first, second, and third workpiecesusing a CCD camera manipulated by a working robot.
 20. The method ofclaim 15, further comprising: applying adhesive to a third workpiece;and pressing the third workpiece against one of the first and secondworkpieces so as to adhere the third workpiece to one of the first andsecond workpieces.